How to reduce PDF file size
Email attachment limits and upload forms often force you to shrink a PDF. Knowing why a PDF is large tells you which method fits.
Published · Guides
Why PDFs get large
- Scans: documents scanned or photographed with a phone hold a high-resolution image on every page.
- Photo-heavy documents: photos inserted at full size take up most of the space.
- Embedded fonts: embedding complete fonts can add several megabytes.
- Edit history: PDFs saved over and over can keep older content inside.
Option 1: keep only the pages you need
If some pages are not needed, removing them with Split PDF or Organize PDF often shrinks the file a lot. It is the surest way to reduce size without losing quality.
Option 2: compress in your browser
AlphaConverter’s Compress PDF rebuilds each page as an image at the quality and resolution you choose. Scans and photo-heavy documents often shrink dramatically, and the file never leaves your device.
- Open Compress PDF and add your PDF.
- Pick a quality and resolution, then convert.
- Check the resulting size; if it is still too big, lower the quality or resolution and try again.
Before you compress
- Selectable text: because pages are rebuilt as images, the compressed PDF’s text cannot be selected or searched. Run Scanned PDF OCR afterwards if you need search.
- Already small PDFs: a small text-only PDF can actually get bigger. Always check the resulting size.
- Keep the original: compression lowers quality, so save the original PDF separately.
Option 3: make it small from the start
- Scan at about 200–300 dpi: easy to read, much smaller than higher settings.
- Shrink photos with Compress Image or Resize Image before putting them into a document.
- When exporting to PDF from Word or other editors, pick options such as “Minimum size” or “Optimize for web” if available.